B'You have two binary strings a and b of length n . You would like to make all the elements of both strings equal to 0 . Unfortunately, you can modify the contents of these strings using only the following operation: Your task is to determine if this is possible, and if it is, to find such an appropriate chain of operations. The number of operations should not exceed n + 5 . It can be proven that if such chain of operations exists, one exists with at most n + 5 operations. Each test consists of multiple test cases. The first line contains a single integer t ( 1 <= q t <= q 10^5 ) -- the number of test cases. The description of test cases follows. The first line of each test case contains a single integer n ( 2 <= n <= 2 cdot 10^5 ) -- the length of the strings. The second line of each test case contains a binary string a , consisting only of characters 0 and 1, of length n . The third line of each test case contains a binary string b , consisting only of characters 0 and 1, of length n . It is guaranteed that sum of n over all test cases doesn 't exceed 2 cdot 10^5 . For each testcase, print first "YES" if it 's possible to make all the elements of both strings equal to 0 . Otherwise, print "NO". If the answer is "YES", on the next line print a single integer k ( 0 <= k <= n + 5 ) -- the number of operations. Then k lines follows, each contains two integers l and r ( 1 <= l <= r <= n ) -- the description of the operation. If there are several correct answers, print any of them. In the first test case, we can perform one operation with l = 2 and r = 2 . So a_2 := 1 - 1 = 0 and string a became equal to 000. b_1 := 1 - 1 = 0 , b_3 := 1 - 1 = 0 and string b became equal to 000. In the second and in the third test cases, it can be proven that it 's impossible to make all elements of both string'...